Gnus: Use new sleep library

* etc/NEWS: Announce.
* lisp/gnus/gnus-start.el: Don't require gnus-dbus.
(gnus-sleep-handler): New function.
(gnus-close-on-sleep): New variable.
(gnus-1): Add `gnus-sleep-handler' to
`system-sleep-event-functions' when `gnus-close-on-sleep' is
non-nil.
* doc/misc/gnus.texi: Update documentation.

doc/misc/gnus.texi

@@ -849,7 +849,7 @@ Various
 * Spam Package::                A package for filtering and processing spam.
 * The Gnus Registry::           A package for tracking messages by Message-ID.
 * The Gnus Cloud::              A package for synchronizing Gnus marks.
-* D-Bus Integration::           Closing Gnus servers on system sleep.
+* System Sleep Integration::    Closing Gnus servers on system sleep.
 * Other modes::                 Interaction with other modes.
 * Various Various::             Things that are really various.
 
@@ -22712,7 +22712,7 @@ For instance, @code{nnir-notmuch-program} is now
 * Spam Package::                A package for filtering and processing spam.
 * The Gnus Registry::           A package for tracking messages by Message-ID.
 * The Gnus Cloud::              A package for synchronizing Gnus marks.
-* D-Bus Integration::           Closing Gnus servers on system sleep.
+* System Sleep Integration::    Closing Gnus servers on system sleep.
 * Other modes::                 Interaction with other modes.
 * Various Various::             Things that are really various.
 @end menu
@@ -26680,11 +26680,11 @@ CloudSynchronizationDataPack(TM)s.  It's easiest to set this from the
 Server buffer (@pxref{Gnus Cloud Setup}).
 @end defvar
 
-@node D-Bus Integration
-@section D-Bus Integration
-@cindex dbus
-@cindex D-Bus
-@cindex gnus-dbus
+@node System Sleep Integration
+@section System Sleep Integration
+@c Section name changed from this in Emacs 31. @c
+@c This anchor allows old links to continue working. @c
+@anchor{D-Bus Integration}
 @cindex system sleep
 @cindex closing servers automatically
 @cindex hung connections
@@ -26692,13 +26692,10 @@ Server buffer (@pxref{Gnus Cloud Setup}).
 When using laptops or other systems that have a sleep or hibernate
 functionality, it's possible for long-running server connections to
 become ``hung'', requiring the user to manually close and re-open the
-connections after the system resumes.  On systems compiled with D-Bus
-support (check the value of @code{(featurep 'dbusbind)}), Gnus can
-register a D-Bus signal to automatically close all server connections
-before the system goes to sleep.  To enable this, set
-@code{gnus-dbus-close-on-sleep} to a non-@code{nil} value.
-
-For more information about D-Bus and Emacs, @pxref{Top,,, dbus, D-Bus integration in Emacs}.
+connections after the system resumes.  Using the system sleep library,
+Gnus can automatically close all server connections before the system
+goes to sleep.  To enable this, set @code{gnus-close-on-sleep} to a
+non-@code{nil} value.
 
 @node Other modes
 @section Interaction with other modes

etc/NEWS

@@ -1967,6 +1967,14 @@ Gnus, see "(gnus) Symbolic Prefixes" in the Gnus manual.
 ---
 *** Sorting selected groups is now possible with 'gnus-topic-mode'.
 
++++
+*** System sleep integration is now independent of D-Bus.
+The system sleep integration previously provided by customizing the
+variable 'gnus-dbus-close-on-sleep' is now deprecated.  A new system
+using the builtin sleep library is now available by customizing
+'gnus-close-on-sleep'.  This will work on all systems that the sleep
+library supports.
+
 ** Sieve
 
 +++

lisp/gnus/gnus-start.el

@@ -31,7 +31,6 @@
 (require 'gnus-range)
 (require 'gnus-util)
 (require 'gnus-cloud)
-(require 'gnus-dbus)
 (autoload 'message-make-date "message")
 (autoload 'gnus-agent-read-servers-validate "gnus-agent")
 (autoload 'gnus-agent-save-local "gnus-agent")
@@ -733,6 +732,22 @@ the first newsgroup."
   ;; Remove Gnus frames.
   (gnus-kill-gnus-frames))
 
+(defcustom gnus-close-on-sleep nil
+  "When non-nil, close Gnus servers on system sleep."
+  :type 'boolean
+  :group 'gnus-start)
+
+(defun gnus-sleep-handler (sleep-event)
+  "Close connection to servers before system sleep.
+See `gnus-close-on-sleep' to enable this functionality.
+
+SLEEP-EVENT is checked to ensure this is only run before sleep."
+  (when (and (eq 'pre-sleep (sleep-event-state sleep-event))
+             (gnus-alive-p))
+    (condition-case nil
+        (gnus-close-all-servers)
+      (error nil))))
+
 (defun gnus-no-server-1 (&optional arg child)
   "Read network news.
 If ARG is a positive number, Gnus will use that as the startup
@@ -800,8 +815,9 @@ prompt the user for the name of an NNTP server to use."
 	  (gnus-run-hooks 'gnus-setup-news-hook)
 	  (when gnus-agent
 	    (gnus-request-create-group "queue" '(nndraft "")))
-	  (when gnus-dbus-close-on-sleep
-	    (gnus-dbus-register-sleep-signal))
+	  (when gnus-close-on-sleep
+            (add-hook 'system-sleep-event-functions
+                      #'gnus-sleep-handler))
 	  (gnus-start-draft-setup)
 	  ;; Generate the group buffer.
 	  (gnus-group-list-groups level)